1. Field of the Invention
The present invention relates to liquefied coffee whiteners comprising vegetable oil. In more detail, the present invention relates to coffee whiteners, which exhibit outstanding emulsification stability on storage without using a synthetic emulsifier, and in which the emulsification dispersibility at the time of adding the coffee whitener to hot drinks, such as coffee, is improved.
2. Discussion of the Background
A coffee whitener is a cream-like oil-in-water emulsion which is used for reducing a bitter taste, an astringent taste, and the like or giving a dense taste by adding it to coffee, tea, and the like. Usually, an edible oil, used as the main material, an emulsified liquid which is added with an emulsifier and, if necessary, added with a milk component, a thickener, flavor, etc. is emulsified by an emulsifying machine such as a high-pressure homogenizer superior in shear force, to thereby prepare the coffee whitener. While many coffee whiteners are kept refrigerated, it is required to be stable such that a separation (oil-off) of fatty oil and a denaturation (feathering) of milk protein due to the addition to hot coffee, tea, etc. do not occur when it is used. In order to secure the stability, usually, synthetic emulsifiers, such as glycerin fatty acid ester, propylene glycol fatty acid ester, sucrose fatty acid ester, sorbitan fatty acid ester, and poly glycerine fatty acid ester, are used so much.
However, the emulsifier has an inherent acerbity, bitter taste, etc., and there is a fault that excellent flavor, taste, and texture of a food to be used are impaired. In addition, generally, the emulsifier has poor solubility, it is necessary to agitate the emulsifier with heating at 60 to 70° C. for dissolving uniformly, and there is also a problem in the work. Furthermore, although a labeling of an “emulsifier” is needed for the food which uses an emulsifier in Japan, in recent years, it has been increased to provide a product without labeling an emulsifier because of an enhancement in consumers' healthy consciousness, so that it is desired to develop a food material which can replace the function of an emulsifier. Therefore, while there have been various attempts for replacing an emulsifier, such attempts are running positively especially in a baking field, however, there is almost no example in a coffee whitener.
So far, various things are indicated about the emulsifier which uses a protein derived from milk (milk protein) such as casein, milk whey protein, etc. as raw materials. For example, there are disclosures as follows: an emulsifier comprised of polypeptide which consists of 5 to 50 amino acids obtained from a reaction product acquired by making proteolytic enzyme act on all the caseins (see Japanese Patent Kokoku Publication No. JP2-968B); a milk protein surfactant characterized in that by making proteolytic enzyme act on milk protein, and partially hydrolyze to a degree of degradation into a range of 5 to 20% (see Japanese Patent Kokai Publication No. JP01-160458A); and an oil-in-water emulsified oil composition characterized by containing a hydrolysate which contains the milk whey protein as the main ingredients hydrolyzed with an enzyme (see Japanese Patent Kokai Publication No. JP02-257838A), etc. In addition, a method has been reported that an emulsification stability of a fat-containing food and the like is increased by combining an emulsifier and casein, for example, there are disclosures of the emulsion stabilizer for milk beverages containing a hydrophilic emulsifier, sodium caseinate and k-carageenan (see Japanese Patent Kokai Publication No. JP06-253735A); an emulsion stabilizer for milk beverages comprising sucrose fatty acid ester, glycerin fatty acid ester, sorbitan fatty acid ester, glycerin succinic acid fatty ester and sodium caseinate as essential ingredients (see Japanese Patent Kokai Publication No. JP-P06-125706A); a method, in which decomposed casein is contained, as an emulsion stabilizer (see Japanese Patent Kokai Publication No. JP-P2003-9785A) etc. However, all are combined use with a synthetic emulsifier, and there are no reports of completely substituting for the function of the synthetic emulsifier in a coffee whitener.
In the meanwhile, a protein deamidating enzyme, which acts directly on an amide group in proteins, is an enzyme which catalyzes a reaction of deamidation. Thereby it causes transformation of glutamine residue into glutamic acid residue to generate a carboxylic group, which results in an increase of negative charge, an increase of electrostatic repulsive force, a decrease of isoelectric point, an increase of hydration capability etc. of protein. As a result, it has been known that various improvements of functionalities such as an increase of solubility of protein and dispersion of protein in water, and an improvement of emulsification ability etc. are afforded (see Yamaguchi et al., Appl. Environ. Microbiol., 66, p. 3337-3343 (2000); Eur. J. Biochem 268 p. 1410-1421 (2001); Japanese Patent Kokai Publication No. JP-P2000-50887A; Japanese Patent Kokai Publication No. JP-P2001-218590A; Japanese Patent Kokai Publication No. JP-P2003-250460A; WO 2006/075772; and WO 2009/154212). In addition, a method of using the protein deamidating enzyme in food products is disclosed in Japanese Patent Kokai Publication No. JP-P2000-50887A; Japanese Patent Kokai Publication No. JP-P2003-250460A; WO 2006/075772; and WO 2009/154212. Among these prior Literatures, there is a description relating to an alteration of functional properties of wheat gluten, milk protein (mainly, whey protein) using the enzyme. It is also disclosed in Japanese Patent Kokai Publication No. JP-P2000-50887A that good dispersbility and solubility and palate were shown when the coffee whitener prepared using the deamidated gluten treated with the protein deamidating enzyme showed a stable emulsion state and it was added to coffee. However, this coffee whitener is what is manufactured using monoglyceride and polysorbate which are synthetic emulsifiers, and it is actually related to the method to improve the solubility and dispersibility of gluten, and it is definitely not suggested to manufacture a coffee whitener in which synthetic emulsifier is not used.
Moreover, the treatment with the protein deamidating enzyme is recognized to effect a change in higher-order structure of protein accompanying the increase in a negative charge of protein and an increase in surface hydrophobicity, and it leads to an increase in an emulsification ability. However, since the casein which is the main milk protein inherently has a random coil configuration with low regularity and amphiphilic structure, it is known as a protein which is more excellent in emulsification ability for many years. Therefore, there are scarcely examples which aimed at an improvement of the emulsifying function of the milk protein using this enzyme anew. It is also disclosed in Japanese Patent Kokai Publication No. JP-P2000-50887A that the deamidated casein shows high solubility under existence of high concentrated calcium. In addition, a method to use the protein deamidating enzyme for yogurt, cheese, and a pudding is disclosed in WO 2006/075772, and a method of manufacturing the starch-containing food, in which color, gloss and texture are good and the time degradation after cooking was controlled, by adding the milk which was treated with the protein deamidating enzyme to a starch-containing food such as bread and sauce is disclosed in WO 2009/154212. However, in the manufacture of the coffee whitener, any example which uses the protein deamidating enzyme has not yet reported so far as an attempt for especially substituting for a synthetic emulsifier.
Thus, there remains a need for improved coffee whiteners.